A Strongly Nonlinear Alfvénic Pulse in a Transversely Inhomogeneous Medium

We investigate the interaction of a plane, linearly polarized, Alfvénic pulse with a one-dimensional, perpendicular to the magnetic field, plasma density inhomogeneity in the strongly nonlinear regime. Our numerical study of the full MHD equations shows that: (i) Plasma density inhomogeneity substantially enhances (by about a factor of 2) the generation of longitudinal compressive waves. (ii) Attained maximal values of the generated transverse compressive perturbations are insensitive to the strength of the plasma density inhomogeneity, plasma β and the initial amplitude of the Alfvén wave. Typically, they reach about 40% of the initial Alfvén wave amplitude. (iii) Attained maximal values of the generated relative density perturbations are within 20-40% for 0.5 ≤ β ≤ 2.0. They depend upon plasma β strongly; and scale almost linearly with the initial Alfvén wave amplitude.